Pneumatic tire and method of making the same



Sept. 22. 1925A Patented Sept. 22, 1925.

UNITED STATES wel.,

PATENT OFFICE.

IRVIN R. RENNER, 0F AKRON, OHIO, ASSIGNOR T0 THE B. F. GOODRICH COMPANY, OF

NEW YORK, N. Y., A. CORIOBATION OF NEW YORK.

PNEUMATIC TIRE AND METHOD OF MAKING THE SAME.

Application led April 14,

To all 'Lc/tom z' may concern Be it known that I, InvIN R. RENNER, a citizen of the United States, residing at Akron, in the county ot Summitand State oi' Ohio, have invented a certain new and useful lneumatic Tire and Method ot' Making the `dame, ot which the tolloiving is a spceitication. ,l

This invention relates to pneumatic tires having a. carcass of thread or cord and rubber construction vulcanized in oblate, oval, cross-scctiomil torni instead of the usual substantially-circular section, the tire liaving bulged side-Walls, giving the working,` portion a greater Width than the Width oi the base within the rim.

The main object.- ot' the invention is to provide a pneumatic tire or tire-Casing oi the type referred to, having no undue thickening' ot the walls in any working part., which will have high load-sustaining power and great endurance atr moderate inflation pressure, together with increased lateral stability as compared with ordinary pneumatic tires of the same base Width, and a less abrupt tlexure of thev side Walls under a given load and inflation.

According to this invention, the tire oarcass is: made to retain a pronounced oval or elliptical shape when inflated to service pressure. ll'hereas, formerly it has heen .sought to obtain this result with inextensible bands or other special construction in the tread wall, in the present invention the oval inflated shape is realized principally or entirely by the use of bias threads laid at suitable angles to the circumferential tread `and side lines ot the tire. The radial depth of the carcass when inflated is at least as great as when the tire is vulcanized, and the rubber and vfabric therein are accordingly not so over-strained as to cause ply sel'iaration and other ill etlects by the bending o'l' the tire wall under load.

Ot the actzompanying drawings:

Fig. l is a side elevation of a tire embodying my invention in a preferred form, parts being sectioned and broken away.

Fi 2 is a plan view of the same, with the tire-core therein, parts being sectioned and broken away.

Referring to the drawings, 10 (Fig. 2) is an annular, laterally bulged, tire core of Whichthe outer peripheral surface or tread 1924. Serial No. 706,538.

portion is substantially flat, transversely, and l2, 12 are superposed plies of Weftless cord fabric constituting a tire carcass upon said core. The usual weak-wetted fabric could of course be used instead of wettless fabric. The threads in succeeding plies are oppositoly biased. as is customary. 'lhe particular tire here shown, being of the straight bend type, comprises inextensible liead-cores 13, 13. but my invention is not limited to straight bead tires. ll'ide breaker strips 14, ll, to correspond to the wide form of the tire, are interposed between the wide tread, l5, and carcass ol' the tire. All parts ot' the tire are prepared and applied to the core in accordance with practice now standard in the building, of tires ot circular section. except that instead ot cutting the fabric on the usual bias ol about l5@ l so cut it that the. cords thereof are disposed at a substantially smaller angle to the longitudinal axis and side edges ol the tire strip. l have found that l can safely reduce the angle ol' the cords in the tread portion ot' the tinished tire to considerably less than 40 to the longitudinal axis of the strip. and thereby maintain a pronounced elliptical cross-sectional :t'orin in the inl'lated tire, the longitudinal stretehability oi the tread wall being' so small as to prevent it from being moved out radially to any great extent by the air pressure.

I preferably cutl the fabric. on an angle of about 35Q to the cords,` forni an endless band from pieces so cut, and stretch it onto the core, the band beingT of such size as to call for a substantial stretch thereof in mount-ing it upon the tread portion of the core. The stretching?)- ot' the band reduces the angle of theI cords with relation to its median line, the band of course becoming narrower as it elongatcs, While the stitching down oi the side margins of the band results in the cords therein assuming a greater angle to the bead, as will be more fully described hereinafter. Thus l obtain in the finished tire an angle preferably ot' about- 33 to the median line in the`tread portion, as shown in Fig. 2, and with the cords disposed at this angle in the tread portion I have obtained tires of pronounced elliptical cross-sectional form under inflation without the developmentof excessive local stresses therein, the ratio of major to minor axes of the ellipse in the carcass of the tire here shown being' 'approximately Q to l.

The tire fabricv` being rolled down to the bead in the usual manner, is somewhat elongated in a direction radial ot' the tire, troni the neutral" line, or line corresponding tothe circumference ot' the band before it is stretched onto the core7 to the bead, and correspoinlingly shortened lon, itinlinallwvv ot the tire, with a progressive increase of these ell'ects l'roni such neutral line to the bead, and this gi\ es the cords at the bead a greater angle to a tangent ot' the bead line than they had to the edge of the llat Strip, and ol' course a greater angle than they have to the median line ot the tread, the longitudinal stretching ot the band onto the core having in the tread region decreased the angle ot the cords to the median line. Thus the angle at the bead may be as large as 55C, as shown in Fig. l, when the angle at the tread illf'. as shown in Fig. 2.

Ass-inning the core l0 to be of rigid, sectional construction, the tire and core may be placed in an outer inold of suitable forni or may be cross-wrapped with cloth, and then vulcanized7 but in accordance with the niore usual practice in the manufacture of cord tires, l prefer to remove the forming core troni the raw tire, insert a Water bag or air bag ot' siinilar forni7 place the tire and bag in a inold having a cavity sonrewhat larger than the bodyy of the tire and expand said tire against the mold by means ot' internal fluid pressure during vulcanization. The tinal shape ot the tire is deterniined by that. oi the inold cavity, which ap proxiniatcs the shape in which the tire is laid up on the t'orin or core lO.

The tread wall of the tire when inflated on the wheel takes a slightlyv arcuate form. I may forni the tread-wall with a slight curvature on the core, instead of tlat, and prefer to do so in tires for lighter vehicles, as will be understood Without special illustration. n

Instead of using a forming core, lay up the tire in lat band form, expand the raw band to tine shape by fluid pressure while drawing-fthe beads together in accordance with a known practice and then vulcanize it. in the elliptical torni described. Other modifications could be inade without departing from iny invention.

B v cutting the fabric at. an angle ot substantialliv less than 450 toits edges, forining the tire as described and vulcanizing it in oblate, oval forni, I secure the advantages mentioned in the introduction. An elliptical tire of ample strength and durability may be obtained, having comparatively thin and flexible walls, by the use of the same nuiterials as in an ordinary tire, formed by operations which are now standard,and with I may but little n'iodilication ot the usual equipnient.

Increased lateral stability results l'roin the sinalle'angleot the threads. espeeiall)Y when the tire not only is vulcanized in an oblate, oval torin, but is iliade to retain essentialh that forni when inflated. Yfhe side walls in a tire ot this type iiex less sharply under load than in a tire ol' the ordinary tvpe, the llexure beingl distributed over a longer arc on the peripher)v oll the wheel.

'l`he angle at which the threads lie with respect to the edgc= ole the lint 'i'abric strips before incorporation in the tire. as well in. the angle which they assume in the linished tire may vary inorc or less from the exainple given, depending on the chosen ratio ol the major and niiuor axes o`l the oval in the linished tire and also on the iuethod einploved in iorniing the. tire. whether shaped around a core, with vanving positions ot the neutral line ot' the original llat band with relation to the core. or shaped b v expanding the middle of a tlat baud Vtroni substantiallj.'v the bead dianieter as in the inodilieation above described, the latter being generally known as the llat band" method to distinguish it ironi the core"` inethod. Starting with the saine angle oi cut, the flat band method results in a. smaller' angularlvvY of the threads in the .finished tire than the core niethod, and such angularily is less in all working parts of the tire than the angularitvv ol the threads in the original band.

The core'i inethml` as herein illustrated. is preferred t'or large tires having a ratio of major to iniuor axes of the inflated` oval carcass ot l; to l or greater` adapted 'For use on wide riins. as the stitching down ol' the careass-forniingbands. cut as described. gives an singularity ol' the threads al the beads greater than the angle of eut, and this in conjunction with the small angle at the tread, preserves the desired ratio of the axes without setting up undue strains in the carcass during operation.

It is known that a small angle for thel threads, especially as normally found in a tire inade buv the Hat band inethod when the bands are cut at an angle of 45 or less, tends to prod uee an oblate, oval forni in an inflated tire which has its carcass vulcanized in substantially circular torni, butthis etlect has heretofore been a disadvantage, tending to cause undue strains and plv separat-ion in the carcass. In the present invention, by vulcanizing in oblate, oval form, a tire having its threads disposed at an angle tending to retain the oval t'orin. I avoid or minimize these strains and produce a tire which can safely be run at a lower inflation pressure t'or a. given load.

I claim:

1. A pneumatic tire having a laminated carcass of oppositel '-biased threads and ruhhcr vulcanized in nhlate, oval, cross-sectional l'orm. the threads haringY an angularity, which in the tread portion is less than 4U" to the middle circumferential line, tendin e to maintain said carcass in the oral form when inflated.

2. A pneumatic tire according to claim l, whose radial depth when inflated is at least as great as when not inflated.

.i headed pneumatic tire casing with hulging sides. having a laminated carcass vulcanized in ohlate, oval, cross-sectiomil form and made ot' crossed rubberized tln'eads extendingr ohhquel)` throughout their length trom head to head. the threads in the tread portion having an angle to the middle circumferential line ot less than 40 and the threads at the beads having an angle greater than the angle in the thread portion.

4. A pneumatic tire casing according to claim 5S, having;r a carcass made from plies ot rubberized tl'ireads which, when the plies are flat, lie at an angle to their edges not greater, substantially, than 40, said carcass heilig of ohlate. oval section hoth when deflated aud when inflated.

A headed pneumatic tire having a corcass i ulcanized in a pronounced olilate, oval twas-sectional form and maintained substantiall)7 in said form, when inflated, essentiall)Y h v reason of the angularitgv ot' its diagonal threads. said carcass comprising opi/ositely-liiascd lilies of ruhlierized threads extendingr diagonally throughout their length from head to head, the threads havingr. in the tread. an angularity of less than 2,50 to the middle circuu'iferential line and having; at the beads. a greater aligrularity to the edges ot the casing.

(l. headed pneumatic tire casing` having a laminated carcass of oppositely-biased Qs. ariatosous Mss., i

threads and ruhher vulcanized iu ohlate.

oval, crosssectioual torni aud adapted to maintain the oval torni when inilatcd sentially hy reason of the anaularly ot its diagonal threads, the inflated carcass harinaY a ratio of major to minor axes as great as. approximately, 4t to ifs. the threads having an angle in the tread ot not more than 255 to the middle circumferential line and an an- `ele at the heads greater than 50.

T. The method ol making' pneumatic tires which comprises building the carcass with ruhherized. oppositely-hiased thread plies having an ohlate.l oval-torndu;r angularity ot threads to the circuniferential lines: ot the tire. which is less in the tread than in the side-walls. and not siihstantially lgreater than 40 in the tread and rulcanizin; r the carcass in oblate, oral. cross-sectional form.

S. The method ot making,r pneumatic tire casings which comprises buildingr the carcass on a core ot' oblate. oral` cross-sectional form7 with oppositely-hiased strips ol ruhlierized threads in which the. threads. when the strips are flat, lie at au angle, to the edges nl* hetwcen 3U@ and 400. stretching the plies at the tread and condensincr them at the sides. t'ormiugr head edges on the. carcass. and rulcanixiuc the casingr in ohlate. oval form with hulgiug sides substantially tarthe' apart than said head edges.

9. Steps in the method ol uuilcing' the tire casingdefined in claim G which comprise formingr the carcass 'from hands cut at an angle of less than 400 to the threads.l stretching said bands at the tread onto a core of olilate Oral section. and stitching them down to the heads at the sides ot the core.

In Witness whereof l have hereunto set my hand this 2nd dayv of April, 1924:.

IRVIN R. REi TNER. 

